Best way to handle an indexing axis

I am adding a horizontal router to my Z axis, which has the ability to rotate 180 degrees. I plan to handle the indexing (0, 90, and 180 degrees) externally with ladder logic, what is the best way to interface this with Mach? Should I use M codes and somehow wait for a finish pulse? Ideas are much appreciated!
Joe

I had a thought, how about handling this like a toolchanger? T2 would be horizontal spindle at 0deg, T2 at 90deg, etc. Somehow I could write a macro in Mach to tell the PLC to index to a certain position, then wait for finish signal.